If you're using Facebook, you've probably seen a lot of posts like this lately:

I bet you can't name a fish that doesn't have the letter A in it. Can you name a band that has no letter T anywhere in their name? This is harder than you think! Post your answers below and share with friends!

If you've put any thought into these questions, you know that they aren't that difficult. So what's the point of them? To understand that, you need to know about Facebook's EdgeRank.

How Facebook decides what you see Just because you have liked a brand's Facebook page doesn't mean that you see all of their posts in your news feed, even if you're on every day. If you are an administrator of a page, you've definitely seen this from the other side. You might have 500 fans, but if you look at the post when you're on your business page, you'll see that it was only shown to 47 of them.

Besides fees for promotion (a whole 'nother topic that I'll discuss later), Facebook uses something called EdgeRank to determine whether you will see a post. They tweak the exact formula all the time, but factors include:

Whether you've interacted with the page before

Whether you've interacted with similar posts in the past

Whether a lot of other people have responded to the post (whether by liking, sharing or commenting on it)

Whether other users have flagged it as spam, or made other complaints

So when that radio station challenges you to name a breed of dog that doesn't include the letter B — I bet you can't do it! — it isn't really about that question; the point is to make their next posts about the upcoming music festival or the new morning show visible to a higher percentage of their fans.